Glossary

Glossary of key terms related to coal-fired power plants:

  • Baghouses:A generic name for air pollution equipment which uses a range of filter bags/fabric types to separate particulate (dust, ash, powders, etc.) from the exhausting air stream. Not only is this an essential process in order to recover the product being manufactured, it is also required by the Environmental Protection Agency (EPA) to ensure that all industrial exhaust gasses are particulate (dust) free, or at least comply with their particulate emission limits. The EPA is particularly concerned with particles that are 10 micrometers in diameter or smaller because those particles generally pass through throats and noses and enter lungs, causing serious health problems.
  • Boiler:A device found in power plants for generating steam for power, processing or heating purposes, or for producing hot water for heating purposes or hot water supply. Heat from an electrical combustion source is transmitted to a fluid contained within the tubes in the boiler shell. The fluid is delivered to an end-user at a desired pressure, temperature and quality. Boilers are often classified as steam or hot water, low pressure or high pressure, capable of burning one fuel or a number of fuels.
  • Carbon dioxide (CO2):A gaseous substance at standard conditions composed of one carbon atom and two oxygen atoms. CO2 is produced when fossil fuels are burned and is thought to be a major contributor to warmer global temperatures.
  • Clean Air Act:A federal law that defines EPA's responsibilities for protecting and improving the nation's air quality and the stratospheric ozone layer. The Clean Air Act Amendments of 1990 were the last major change in the law, enacted by Congress. Legislation passed since that time has made several minor changes.
  • Clean Air Mercury Rule (CAMR):The EPA's March2005 Clean Air Mercury Rule is the first of its kind - and the first in the world - to regulate mercury air emissions from coal-fired power plants. The rule creates a market-based cap-and-trade program that will permanently cap utility mercury air emissions in two phases:
    • The first phase of the rule sets a cap of 38 tons per year for all power plants in the U.S., and is projected to reduce air emissions from 48 tons to 31 tons per year beginning in 2010.
    • Air emissions will continue to decline thereafter until they are reduced to the second phase cap of 15 tons per year when the program is fully implemented. (This regulation was vacated by a federal court in 2008 and a new rule is anticipated in 2011.) To learn more about the CAMR, please click here.
  • Clean Coal Technologies:Processes designed to burn coal with little or fewer emissions, including coal with either high sulfur content or high ash content that might make it unattractive as a fuel.
  • Coal:A fossil fuel and one of the leading energy sources in the U.S. and around the world. As an energy source, coal accounts for approximately 46 percent of energy capacity in the U.S. Physically, it is a black or brownish-black solid combustible substance formed by the partial decomposition of vegetable matter without access to air.
  • Coal additive:A type of substance, either liquid, solid or gas, that is manually added to coal for some altering purpose. Some additives are used to even out coal, alter emissions, improve furnace operation and a variety of other purposes.
  • Coal-fired power plant:A fossil-fuel power station that burns fossil fuels such as coal, natural gas or petroleum (oil) to produce electricity. Central station fossil-fuel power plants are designed on a large scale for continuous operation. In many countries, such plants provide most of the electrical energy used. Fossil fueled power stations are major emitters of CO2, the most harmful greenhouse gas.
  • Combustion:The process of retrieving energy from the burning of fuels in the most efficient way possible. To maximize combustion efficiency, it is necessary to burn all fuel material with the least amount of waste. The more efficiently fuels are burned and energy is gathered, the cheaper the combustion process becomes.
  • Commercial viability:The ability of a product to sustain a customer base and achieve profitability over a long-term basis.
  • EERC:The Energy Environmental Research Center (EERC) is recognized as one of the world's leading developers of cleaner, more efficient energy and environmental technologies to protect and clean our air, water and soil. The EERC is a high-tech, nonprofit branch of the University of North Dakota(UND). The EERC operates like a business; they conduct research, development, demonstration, and commercialization activities, and are dedicated to moving promising technologies out of the laboratory and into the commercial marketplace.
  • Electrostatic precipitator:An electrostatic precipitator (ESP), or electrostatic air cleaner, is a pollution control device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. ESPs are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter, such as dust and smoke, from the air stream. In contrast to wet scrubbers, which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in theform of electricity).
  • Emissions:Substances that are released into the air from power generating plants among other sources. Major emissions that are regulated by the federal government are nitrogen oxide, sulfur dioxide and mercury. Carbon dioxide is also a major emission, but is not regulated. Emissions from power plants and their byproducts form particulate matter, ozone smog and air toxins. These pollutants are associated with a vast array of health concerns such as respiratory hospitalizations, lost school days due to asthma attacks, low birth weight, stunted lung growth and infant death.
  • Flue gas:A gas that exits into the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, it refers to the combustion exhaust gas produced at power plants. Its composition depends on what is being burned, but it will usually consist of mostly nitrogen (typically more than two-thirds) derived from the combustion air, carbon dioxide (CO2) and water vapor as well as excess oxygen (also derived from the combustion air). It further contains a small percentage of pollutants such as particulate matter, carbon monoxide, nitrogen oxide and sulfur oxide.
  • Fly ash:Finely divided particles of ash entrained in gases resulting from the combustion of fuel. Approximately six million tons of fly ash are used each year in the U.S., in major projects such as highway construction.
  • Fossil fuel:Ancient organic remains (fossils) in sediments which over eons became sedimentary rock, giving rise to solid, liquid and gaseous fuels such as coal, crude oil, and natural gas. Coal is derived from vegetable matter altered by pressure, whereas crude oil and natural gas are derived from animal and vegetable matter altered by pressure and heat. Essentially, all fossil fuels are highly concentrated forms of far-ancient sunlight trapped in organic cells. They have been the primary energy source for human societies since the industrial revolution (mid-19th century to early 20th century), are non-renewable and are considered to be a primary source of global warming.
  • Hazardous Air Pollutants:(Also known as air toxins) Chemicals that are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental effects. Listed hazardous air pollutants include benzene, found in gasoline; perchlorethlyene, emitted from some dry cleaning facilities; and methylene chloride, used as a solvent and paint stripper in industry; as well as dioxin, asbestos, toluene, and metals such as cadmium, mercury, chromium and lead compounds.
  • Megawatt (MW):A unit of electrical power equal to one million watts or one thousand kilowatts.
  • Mercury:A metallic element that is toxic to human beings whose emission into the environment has come under increasingly tight restrictions. In 1988 it was estimated that 24 million pounds per year of mercury were released into the air, land and water worldwide as the result of human activities.
  • Nitrogen oxide:A pollutant released into the air when coal is burned. It refers specifically to NOx (NO and NO2). Nitrogen oxides, or NOx, are the generic terms for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts. Many of the nitrogen oxides are colorless and odorless. However, one common pollutant, nitrogen dioxide (NO2) along with particles in the air, can often be seen as a reddish-brown layer over many urban areas. Nitrogen oxide forms when fuel is burned at high temperatures, as in a combustion process. The primary sources of NOx are motor vehicles, electric utilities, and other industrial, commercial, and residential sources that burn fuels.
  • Particulate matter:Fine particles or soot that are tiny subdivisions of solid matter suspended in a gas or liquid. Sources of particulate matter can be man-made or natural. Some particulates occur naturally, originating from volcanoes, forest and grassland fire, for example. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes, also generate significant amounts of aerosols. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.

  • Selective catalytic reduction (SCR):A means of converting nitrogen oxide (NOx) with the aid of a catalyst into diatomic nitrogen (N2), and water (H2O). A gaseous reluctant, typically anhydrous ammonia, aqueous ammonia or urea, is added to a stream of flue or exhaust gas and is absorbed onto a catalyst. Carbon dioxide (CO2) is a reaction product when urea is used as the reductant. Commercial selective catalytic reduction systems are typically found on large utility boilers, industrial boilers, and municipal solid waste boilers and have been shown to reduce NOx by 70 to 95 percent.
  • Scrubber:An apparatus that cleans the gases passing through a stack prior to being emitted. Scrubber systems are a diverse group of air pollution control devices that can be used to remove some particulates and/or gases from industrial exhaust streams. Traditionally, the term "scrubber" has referred to pollution control devices that use liquid to wash unwanted pollutants from a gas stream. They are often used at coal-burning power plants as a pollution control device. Recently, the term is also used to describe systems that inject a dry reagent or slurry into a dirty exhaust stream to "wash out" acid gases. Scrubbers are one of the primary devices that control gaseous emissions, especially acid gases. Scrubbers can also be used for heat recovery from hot gases by flue gas condensation.
  • Slagging:The glass-like mass left as a residue by the smelting of metallic ore.
  • Slurry:A thin mixture of a liquid, especially water, and any of several finely divided substances, such as cement, plaster of Paris or clay particles.
  • Sorbents:Insoluble materials or mixtures of materials capable of adsorption (attracting and holding substances upon its surface [e.g., charcoal]) and absorption (sucking in and holding a substance within a porous material [e.g., sponges]). Sorbents have been used to clean up oil spills and have also been used in coal-fired plants to reduce the amount of mercury and other pollutant emissions. Sorbents can be divided into three basic categories: natural organic, natural inorganic and synthetic.
  • Sulfur dioxide:Also known as SO2, is a pollutant that is released into air through industrial uses including when coal is burned. SO2 has been linked to a number of adverse effects on the human respiratory system including chronic bronchitis and emphysema. Physically, it is a colorless, extremely irritating gas or liquid.
  • Toxicity Characteristic Leaching Procedure (TCLP):TCLP is an EPA test method that is used to characterize waste as either hazardous or non-hazardous for the purpose of disposal. The TCLP analysis is designed to simulate landfill conditions. Over time, water and other liquids permeate through landfills. The "leachate" liquids often react with the solid waste in the landfill, and may pose public and environmental health risks because of the contaminants they absorb. TCLP is an acronym for Toxicity Characteristic Leaching Procedure and is performed by environmental testing labs.